1. Field of the Invention
The present invention relates to a compound, a salt, and a radiation-sensitive resin composition.
2. Discussion of the Background
In the field of microfabrication represented by production of integrated circuit devices, a lithographic process that enables microfabrication with a line width of 0.20 μm or less has been desired to achieve a higher degree of integration. A lithographic process has utilized near ultraviolet rays (e.g., i-line). However, it is difficult to implement sub-quarter-micron microfabrication using near ultraviolet rays.
Therefore, use of radiation having a shorter wavelength has been studied to enable microfabrication with a line width of 0.20 μm or less. Examples of such radiation include deep ultraviolet rays (e.g., mercury line spectrum and excimer laser light), X-rays, electron beams, and the like. In particular, technology that utilizes KrF excimer laser light (wavelength: 248 nm), ArF excimer laser light (wavelength: 193 nm), F2 excimer laser light (wavelength: 157 nm), EUV (wavelength: 13 nm), electron beams, or the like has attracted attention.
As a radiation-sensitive resin composition that is suitable for radiation having a short wavelength, various compositions (chemically-amplified radiation-sensitive compositions) that utilize a chemical amplification effect that occurs between an acid-dissociable functional group-containing component and a radiation-sensitive acid generator that generates an acid upon irradiation (exposure) have been proposed.
For example, Japanese Examined Patent Publication (KOKOKU) No. 2-27660 discloses a composition that includes a polymer containing a t-butyl ester group of a carboxylic acid or a t-butyl carbonate group of phenol, and a radiation-sensitive acid generator. This composition utilizes a phenomenon in which the t-butyl ester group or the t-butyl carbonate group contained in the polymer dissociates due to an acid generated upon exposure to form an acidic group (e.g., carboxyl group or phenolic hydroxyl group) so that the exposed area of the resist film becomes readily soluble in an alkaline developer.
A radiation-sensitive acid generator used for the chemically-amplified radiation-sensitive composition is required to exhibit high radiation transmittance, generate an acid having high acidity in high quantum yield, and ensure that the generated acid has an appropriate diffusion distance (diffusion length) in a resist film, and has high mutual solubility with an acid-dissociable group-containing resin, for example.
In order to generate an acid having high acidity, an appropriate diffusion length, and high mutual solubility with an acid-dissociable group-containing resin, the structure of an anionic moiety (ionic radiation-sensitive acid generator) or the structure of a sulfonyl moiety (nonionic radiation-sensitive acid generator having a sulfonyl structure or a sulfonate structure) is important. For example, a radiation-sensitive acid generator having a trifluoromethanesulfonyl structure or a nonafluorobutanesulfonyl structure generates a sufficiently strong acid so that the resulting photoresist exhibits sufficient sensitivity. However, since the acid generated by such a radiation-sensitive acid generator has a long diffusion length and poor mutual solubility with an acid-dissociable group-containing resin due to a high fluorine content, a deterioration in mask linearity, MEEF, and LWR occurs. On the other hand, a radiation-sensitive acid generator that has a sulfonyl structure bonded to a large organic group (e.g., 10-camphorsulfonyl structure) generates an acid that has a high carbon content, excellent mutual solubility with an acid-dissociable group-containing resin, and a sufficiently short diffusion length so that excellent mask linearity, MEEF, and LWR are achieved. However, since the acid generated by such a radiation-sensitive acid generator has insufficient acidity, the resulting photoresist exhibits poor sensitivity.
Therefore, development of a radiation-sensitive acid generator that may provide a chemically-amplified radiation-sensitive composition that has moderate sensitivity and exhibits excellent mask linearity, MEEF, and LWR in a well-balanced manner has been desired.